This project seeks to determine whether the regulation of lens fiber differentiation and maturaton is associated with alterations in the plasma membrane. The composition, biosynthesis, and metabolism of lens lipids have been investigated using embryonic and adult chicken lenses, and cultured lens epithelial cells derived from the Nakano mouse. The rate of degradation of the membrane phospholipid, phosphatidylinositol, has been shown to be tightly coupled to the rate of lens epithelial cell divisions and to cease when the epithelial cells differentiate to form lens fibers. Since phosphatidylinositol is rich in arachidonic acid, a precursor of prostaglandins and leukotrienes, the metabolities of arachidonic acid produced by lens epithelial cells are being characterized in an effor to understand the physiological role of phosphatidylinositol degradation. Alterations in phosphatidylinositol metabolism and in the production of arachidonic acid metabolities are being correlated with the action of growth factors in regulating cell division and differentiation.